This invention is directed to the field of archery, and more specifically to compound bows of the type employing cams and control cables to achieve a programmed draw weight, and the latter being variable with draw length. Applicant incorporates by reference prior U.S. Pat. No. 6,776,148 and other patents referred to in that document, that is, archery bows that have cams and power cords, and are programmed for optimal draw weight characteristics.
Typically, compound bows have means to regulate their draw weight so that a maximum pull weight is attained at an intermediate draw position, and with the draw weight dropping to some fraction of maximum pull weight at the full draw position.
It is also an objective of modern bows and crossbows to transfer to the bolt or arrow as much as possible of the energy that is stored in the bow, so that the projectile will fly faster and farther for a given draw weight. These goals have been difficult to achieve. Some inefficiencies are due to mechanical losses in the crossover strings and pulley mechanisms.
Unlike the prior designs, the present invention does not obtain the maximum draw weight at a partial draw position and then drop off draw weight at the full draw position. Instead, the bow or crossbow is designed so that draw weight increases continuously to full draw. This characteristic is required in some forms of long bow archery, and is useful in crossbow archery, because the crossbow has a mechanical release that holds the bowstring at full draw. Because the crossbow does not have to allow for drop-off of pull weight, there is no need for synchronizing cords or strings, and no need for cross-over strings.